1. Field of the Invention
The present invention relates to an apparatus which realizes a displaying function and an imaging function.
2. Description of the Related Art
FIG. 27 shows a typical prior art. A picture telephone 1 includes a personal computer 2 and a television camera 3. The personal computer 2 includes a personal computer main unit 4 including a central processing unit, a key board 5 which has ten numerical keys for manipulation, and a display apparatus 6 such as a cathode ray tube. The display apparatus 6 receives an image, such as the face of a conversation partner who is on the picture telephone, through a telephone line, and displays the image. The face of an operator who uses the picture telephone is imaged by the television camera 3 which is disposed above the display apparatus 6, and a signal expressing the face is sent through the telephone line. Further, in relation to the personal computer 2, a speaker 7 for a television audio output and a microphone 8 for sending the operator's voice are disposed.
According to the prior art as shown in FIG. 27, since the operator looks at a screen of the display apparatus 6, the television camera 3 always images the operator with his head down. The television camera 3 cannot image an expression on the full face of the operator as he is seen head-on, which in turn degrades the function of the picture television.
Another prior art is disclosed in Japanese Unexamined Patent Publication JP-A 5-14880 (1993). According to this prior art, a solid-state imaging device formed by a two-dimensional image sensor using a charge coupled device (abbreviated as "CCD") is disposed to a side portion of an image display apparatus. The solid-state imaging device images the face of an operator who looks at a display screen slightly from a side angle, but cannot image the full face of the operator.
Still another prior art is disclosed in Japanese Unexamined Patent Publication JP-A 6-245209 (1994). In a camera-integrated display apparatus disclosed herein, a hole is formed in a polarization plate which is disposed in the back of a liquid crystal display portion so that light entering through the hole is allowed into a television camera for imaging.
This prior art is advantageous in that the television camera can image the full face of an operator who looks at the liquid crystal display portion. However, since the polarization plate includes the hole for guiding light into the television camera, an image displayed on the screen is defective.
Still other prior arts are disclosed in Japanese Unexamined Patent Publication JP-A 1-106467 (1989) and 5-276313 (1993). These prior arts are connected to a personal computer, a word processor or the like to enable a function of reading an original by contacting with the original and displaying an image.
Hence, when these prior arts are applied to a picture telephone, etc., it is not possible to image an object, such as an image of an operator of the picture telephone, which is far away from an imaging position, and therefore application is limited.
In a prior art imaging apparatus, a field stop mechanism which has a mechanical structure with a variable aperture diameter realizes adjustment of the amount of light incident upon an imaging element, namely, adjustment of exposure. It is clear that such a structure inevitably requires the imaging apparatus to be large. This is a main impediment to saving of product cost.
In a prior art image sensor, such as a CCD, which has a so-called electronic iris function, an electronic shutter controls the light-receptivity. This is different from a full-fledged exposure adjusting function.